Datasheet

SN54ABT18245A, SN74ABT18245A
SCAN TEST DEVICES
WITH 18-BIT BUS TRANSCEIVERS
SCBS110H – AUGUST 1992 – REVISED FEBRUARY 1999
10
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
bypass register
The bypass register is a 1-bit scan path that can be selected to shorten the length of the system scan path,
reducing the number of bits per test pattern that must be applied to complete a test operation. During
Capture-DR, the bypass register captures a logic 0. The bypass register order of scan is shown in
Figure 4.
Bit 0
TDOTDI
Figure 4. Bypass Register Order of Scan
device-identification register
The device-identification register (IDR) is 32 bits long. It can be selected and read to identify the manufacturer,
part number, and version of this device.
During Capture-DR, the binary value 00010000000000000101000000101111 (1000502F, hex) is captured in
the IDR to identify this device as Texas Instruments SN54/74ABT18245A. The IDR order of scan is from TDI
through bits 31–0 to TDO. Table 2 shows the IDR bits and their significance.
Table 2. Device-Identification Register Configuration
IDR BIT
NUMBER
IDENTIFICATION
SIGNIFICANCE
IDR BIT
NUMBER
IDENTIFICATION
SIGNIFICANCE
IDR BIT
NUMBER
IDENTIFICATION
SIGNIFICANCE
31 VERSION3 27 PARTNUMBER15 11 MANUFACTURER10
†
30 VERSION2 26 PARTNUMBER14 10 MANUFACTURER09
†
29 VERSION1 25 PARTNUMBER13 9 MANUFACTURER08
†
28 VERSION0 24 PARTNUMBER12 8 MANUFACTURER07
†
  23 PARTNUMBER11 7 MANUFACTURER06
†
  22 PARTNUMBER10 6 MANUFACTURER05
†
  21 PARTNUMBER09 5 MANUFACTURER04
†
  20 PARTNUMBER08 4 MANUFACTURER03
†
  19 PARTNUMBER07 3 MANUFACTURER02
†
  18 PARTNUMBER06 2 MANUFACTURER01
†
  17 PARTNUMBER05 1 MANUFACTURER00
†
  16 PARTNUMBER04 0 LOGIC1
†
  15 PARTNUMBER03  
  14 PARTNUMBER02  
  13 PARTNUMBER01  
  12 PARTNUMBER00  
†
Note that for TI products, bits 11–0 of the device-identification register always contain the binary value 000000101111
(02F, hex).